1. Field of the Invention
The invention concerns a method to determine the projection geometry of an x-ray system.
2. Description of the Prior Art
In medical practice, it is common for one x-ray image or multiple 2D x-ray images of a patient to be acquired within the scope of many types of medical interventions. For example, these images serve for: model-based 3D calculation from a few projection images; the determination of a 3D attitude of an implant or tool introduced into the patient relative to tissue or a bone of a patient; or the image fusion of 2D x-ray images with preoperatively or intraoperatively measured 3D data sets.
For all these applications it is necessary to determine or to calculate the acquisition parameters with which the 2D x-ray images were generated. In other words, the projection geometry or acquisition geometry of the x-ray system used in the generation of the 2D x-ray image must be determined.
For example, in order to determine the acquisition geometry in 2D x-ray exposures it is known to use a position detection system or navigation system. It is also known to use stationary marker systems, for example marker systems that are attached to the patient and that have a known geometry.